Studies on polymerization of higher α-olefins having 10 or more carbon atoms predominantly using Ziegler-Natta catalysts have already been conducted (for example, Japanese Unexamined Patent Application Publication No. 7-145205, Polymer J., 10, 619 (1978), Macromol. Chem., 190, 2683 (1989) and Makromol. Chem., Rapid Comm., 13, 447 (1992)).
However, these higher α-olefin polymers disclosed by the above documents are observed to be inhomogeneous such that the molecular weight is low, the melting point is high owing to high regularity, or two melting points appear in one polymer material.
Furthermore, it is also disclosed that higher α-olefin polymers can be obtained by using homogeneous catalysts called metallocene catalysts (For example, Macromol. Sci. Pure Appl. Chem., A35, 473 (1998), J. Polym. Sci. A, 38, 233 (2000), Macromol. Mater. Eng., 286, 350 (2001) and Macromol. Mater. Eng., 286, 480 (2001)).
However, the above-mentioned polymers do not have sufficiently high molecular weights and appear to be inhomogeneous such that the melting point is high owing to high regularity and also that two melting points appear in one polymer material, being similar to the polymers obtained by using heterogeneous catalysts.
Presence of a plurality of melting points appearing in one polymer material represents inhomogeneity in the size of crystals or the like, possibly causing tackiness.
When such a polymer is mixed with other materials to be used as a modifying agent, homogeneous blending may not be carried out, and desired modified properties may not be obtained.
Further, for the use as a heat storage material, it is preferred for a material to have rapid heat dissipation and absorption resulting from rapid melting or crystallization at a specific temperature with regard to efficiency improvement, and thus it is difficult to use an inhomogeneous resin for the purpose.